A wide variety of soil release agents (s.r.a.'s) for use in in-home fabric treatment processes such as laundering, fabric drying in hot air clothes dryers, and the like are known in the art. Various s.r.a.'s have been commercialized and are currently used in detergent compositions and fabric softener/antistatic articles and compositions. Such s.r.a.'s typically comprise an oligomeric ester "backbone" and one or more "end-capping" units.
While nonionic s.r.a.'s are known in the literature, many of the commercially important s.r.a.'s are anionic. Such anionic s.r.a.'s typically comprise an oligoester backbone which may itself optionally contain various anionic substituents and will usually terminate with one or more end-capping units which are also anionic. For example, various oxy-alkylene/terephthalate/sulfoisophthaloyl oligomers end-capped with sulfoaroyl substituents comprise a known and important class of s.r.a.'s for use in laundry detergents.
Unfortunately, the manufacture of s.r.a.'s having sulfoaroyl end-caps is expensive due to the expense of the sulfoaroyl raw materials. Accordingly, it is of substantial interest to the manufacturers of anionic ester-type s.r.a.'s to find a less expensive type of anionic end-capping unit. It would have appeared that isethionate-derived substituents of the type --OCH.sub.2 CH.sub.2 SO.sub.3 --or poly-ethoxy or propoxy derivatives might be ideal, and less expensive, substitutes for the sulfoaroyl end-capping units. This is particularly true since the terminal hydroxyl groups of this family of hydroxysulfonates can undergo an esterification reaction with the oligomeric ester backbone of the s.r.a. However, it transpires that, during synthesis of s.r.a.'s with isethionate (2-hydroxyethanesulfonate) units or modified poly-ethoxy/propoxy sulfonated end-caps, substantial difficulties can occur due to undesirable crystallization of the s.r.a.'s and/or the end-cap units.
It has now been discovered that the mixtures of sulfonate-type hydrotropes, alkylbenzenesulfonates, or paraffin sulfonates with the soil release oligomer reduces the crystallization problems encountered in certain preferred di-capped s.r.a.'s during manufacture and storage as well as when the s.r.a.'s are introduced to the wash liquor.
It is an object of the present invention to provide novel, less expensive di-capped s.r.a compositions which can be used as inexpensive, effective and product-compatible soil release agents in consumer products having widely varying formulas, such as granular detergent compositions and laundry detergent bars.
These and other objects are secured herein as will be seen from the following disclosure.